Perinereis Kinberg 1865

Key to Atlantic Perinereis species (excluding the Mediterranean Sea) 1,4

1. A single bar-shaped paragnath on each area VI ................................................................................ 2

– Two or more bar-shaped paragnaths on each area VI ..................................................................... 12

2. Lacking paragnaths in area V ....... P. capensis (Kinberg, 1865) (Cape of Good Hope, South Africa)

– Having paragnaths in area V ............................................................................................................. 3

3. A single paragnath in area V ............................................................................................................. 4

– More than one paragnath in areas V ................................................................................................11

4. Tentacular cirri extending back up to chaetiger 4 (i.e., short tentacular cirri) .................................. 5

– Tentacular cirri extending back beyond chaetiger 6 (i.e., long tentacular cirri) ............................... 9

5. One or two paragnaths in area I ........................................................................................................ 6

– Three or more paragnaths in area I ................................................................................................... 8

6. Areas VII–VIII with a single broad band with several rows of paragnaths (> 100 paragnaths) ......... ............................................................................... P. falklandica (Ramsay, 1914) (Falkland Islands)

– Areas VII–VIII with 3–4 rows of paragnaths (about 19–43 paragnaths) ......................................... 7

7. Paragnath in area V aligned with bars in areas VI, forming a straight row; each bar in areas VI almost as long as wide as area VI (i.e., long bars) ................................ P. oliveirae (Horst, 1889) (Portugal)

– Paragnath in area V displaced backward, not aligned with bars in areas VI; each bar in areas VI up to half as long as wide as area VI (i.e., short bars) ................ P. atlantica (São Vicente, Cape Verde)

8. Dorsal ligules 2.3× as long as median ligules and ventral ligules shorter than neuroacicular ligules in posterior chaetigers ........................................... P. ponteni Kinberg, 1865 (Rio de Janeiro, Brazil)

– Dorsal ligules 3.3× as long as median ligules and ventral ligules longer than neuroacicular ligules in posterior chaetigers .................................................................. P. bairdii (Webster, 1884) (Bermuda)

9. Dorsal cirri subequal or shorter than distal lobes of dorsal ligules and ventral ligules longer than neuroacicular ligules in posterior chaetigers ...................................................................................... ................................................................... P. floridana (Ehlers, 1868) (Captiva Key, Florida, USA)

– Dorsal cirri longer than distal lobes of dorsal ligules and ventral ligules shorter than neuroacicular ligules in posterior chaetigers ......................................................................................................... 10

10. A single paragnath in area I; ventral cirri shorter than ventral ligules in posterior chaetigers ........... ................................................................ P. falsovariegata Monro, 1933a (Preekstoel, South Africa)

– Three or more paragnaths in area I; ventral cirri longer than ventral ligules in posterior chaetigers. ............................................................................................................ P. websteri sp. nov. (Bermuda)

11. Two bands of paragnaths in areas VII–VIII; dorsal ligules several times longer than median ligules in posterior chaetigers ..................................... P. anderssoni Kinberg, 1865 (Rio de Janeiro, Brazil)

– A single band of paragnaths in areas VII–VIII; both dorsal and median ligules subequal in posterior chaetigers ........................................... Perinereis taorica Langerhans, 1881 (Canary Islands, Spain)

12. Nine to ten bar-shaped paragnaths on each area VI ............................................................................ ................................................... P. latipalpa (Schmarda, 1861) (Cape of Good Hope, South Africa)

– Two bar-shaped paragnaths on each area VI .................................................................................. 13

13. Paragnaths absent in area V; posterior band of paragnaths in areas VII–VIII discontinuous ............. ................................... P. cariboea de León-González & Solís-Weiss, 1998 (Quintana Roo, Mexico)

– Paragnaths absent in area V; posterior band of paragnaths in areas VII–VIII continuous ............. 14

14. Notopodial prechaetal lobes present at least in anterior chaetigers; rows in areas VII–VIII with paragnaths of distinct size ................................................ P. brevicirrata (Treadwell, 1920) (Brazil) 2

– Notopodial prechaetal lobe absent; rows in areas VII–VIII with paragnaths of similar size ......... 15

15. Distal lobes of dorsal ligules subequal or shorter than medial ligules in posterior chaetigers; blades of neuropodial falcigers with rod-like tips .......................................................................................... ................................... P. rookeri de León-González & Goethel, 2013 (Rookery Bay, Florida, USA)

– Distal lobes of dorsal ligules longer than medial ligules in posterior chaetigers; blades of neuropodial falcigers with falcate tips .......... P. mochimaensis Liñero-Arana, 1983 (Mochima Bay, Venezuela) / .................................................. P. cariacoensis Liñero-Arana, 1983 (Golfo de Cariaco, Venezuela) 3

1 Nereis marionii Audouin & Milne Edwards, 1833 (type locality: Vendée, France) (synonyms: P. longipes de Saint-Joseph, 1898 from Guettary, France, and Nereis crassipes de Quatrefages, 1866 from Normandy, France) and N. aculeata Hansen, 1882 (type locality: Brazil) are excluded from the key. Nereis marionii differs in several pharyngeal and parapodial features from Perinereis species, such as having a continuous band of paragnaths in the oral ring, and the presence of notopodial prechaetal lobes and additional upper lobe in dorsal ligules (Audouin & Milne-Edwards 1833; Fauvel 1923), so likely it belongs to a distinct genus. The original description of Nereis aculeata is succinct (Hansen 1882) and allows to identify it as a Perinereis, but further study is needed to determine if it is a valid species.

2 Treadwell (1920: fig. 2) described a parapodium from chaetiger 10 (likely depicted upside down in his figure) with three notopodial ligules. The species needs further re-evaluation to ensure it is a Perinereis species.

3 As pointed out by de León-González & Goethel (2013), both species are very similar. Both species were proposed based on a single specimen each (even one of them incomplete), and differences in head and parapodial morphology between them are very subtle. Chances are that the transverse bar in area V is due to the partial merging of two or more conical paragnaths like in melted paragnaths, which have been observed in some specimens of P. websteri sp. nov. in additional paragnaths in areas VI. A revision of the type and additional material of both species is needed to clarify their validity.

4 References consulted: Horst (1889); Treadwell (1920); Monro (1933a); Hartman (1938b); Day (1967); Liñero-Arana (1983); de León-González & Solís-Weiss (1998); Núñez (2004); de León-González & Goethel (2013); Darbyshire (2014); Coutinho et al. (2015); Paiva et al. (2018); Villalobos-Guerrero (2019).